Selective two-step photoionization of F-aggregate centers using 106-μm radiation

Abstract
A two-step photoionization of several potentially laser-active F-aggregate centers is observed in additively colored crystals by using high-intensity 1.06-μm pulses from a Q-switched Nd:YAG laser. The centers produced include the lithium (F2+)A center in KI, which has lased with tunability from 2.4 to 4.0 μm, and N1+ centers in KBr, which show promise of lasing. Steady-state concentrations of ionized (F2+)A and N1+ centers are found to be considerably larger than those produced by using blue or near-ultraviolet excitation.